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Best practices for 12"x24" exterior, vertical tile; cold weather tiling; excessive glue on mosaics sheets
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Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Team. To become a member and make use of personal, targeted answers from NTCA's Technical Team to your installation questions, contact Jim Olson.
I’m looking for the best practices and/or products recommended for the following application, and what we need to look out for.
  • Product: 12" x 24" Porcelain
  • Quantity: 14,000 sq.ft.
  • Application: Vertical tile on CMU Tilt Up. Height from 0' to 44'
  • Install Season: Las Vegas June 100 to 110 degrees varying
Example image: Serendipity in 12"x24" by Florida Tile.
Training Director Mark Heinlein and NTCA Trainer Randy Fleming addressed this situation with the member via phone. These aspects of the job were discussed with the member.
  • Temperature of setting materials, tile, substrate and techniques to keep them within a proper working temperature range.
  • Scheduling work flow to take advantage of time of day temperature cycles and movement of the sun/shade.
  • Techniques to shade the substrate and installation work area.
  • Techniques to ensure cool water for mixing.
  • Selecting adhesives for an extended open time/long pot life.
  • Mixing location of adhesive to aid in pot life.
  • Applying a membrane to prevent the dry substrate from drawing the water of the adhesive.
  • Working with the preferred setting material manufacturer as a partner to select the correct adhesive and membrane and to understand proper mixing, application and open time.
  • Preparing the substrate to ensure all bond breakers/curing compounds are removed and to create the required concrete surface profile for bonding.
  • Identifying the appropriate TCNA Handbook method to be used (likely W202E) and the installation standards and material specifications it references.
  • Requiring the specifier to provide drawings/details for installation/location/materials for movement joints as described by EJ171.
QUESTION Our customer is asking us to install tile on an interior application with no windows or heat in a temperature of 27 degrees Fahrenheit. I’m looking for some documentation to explain why this isn’t a good idea.
ANSWER This is a terrific question to ask and I am glad you see the low temperature as a red flag to correct before installation.
Please take a look at your copy of the 2022/2023 edition of the NTCA Reference Manual. Go to Chapter 7, Cold Weather Tiling, on page 142 (see image attached here). This should answer all of your questions.
– Mark Heinlein, NTCA Training Director
QUESTION I am putting down a 1" hex marble mosaic floor for a customer. I saw excessive glue on a number of sheets, which I set aside.
I wanted a sheet’s worth of pieces available to me to fill in a narrow spot on the floor, so I put a sheet in warm water to soak. That is when I realized that the glue issue may be much worse than I originally thought.
  • Picture 1 has three pieces, one cleaned of the glue, the other not, and one partially cleaned.
  • Picture 2 is the sheet in the water with the mesh still partially attached.
  • Picture 3 has the mesh completely removed, but the impression is still visible.
If this is what these sheets are like, I do not relish the idea of putting them down. They are expensive and are what the customer wants.

Do you have suggestions as to how to proceed? I do not want to have to lay this floor (75-80 sq. ft.) one hex at a time, but the excess glue does not give me confidence in the sheets either.
Am I being overly cautious?
Picture 1
Picture 2
Picture 3
I have been discussing this project with this member off and on for several weeks now. He is making good progress and has received some good advice along the way. He followed NTCA advice and made both a floor mock up and wall mock up before starting this project, which really impressed the general contractor.
After grouting the mock up, he discovered that the grout stains the marble, so he decided to follow Robb Roderick‘s guidance in his YouTube video on Six Sided Sealing the stone, found on the NTCA YouTube channel. Today we talked about the glue used in the mosaic sheets and his concerns about that. (This mosaic is in a dry area only). We talked about the decisions and risk tile contractors have to decide whether they are willing to take or not. While on the phone, we decided he should do a destructive test, trying to pull the mosaic off of his mock up. This gave him the confidence he needed to move forward after seeing how well it was bonded.
– Matt Welner, NTCA Trainer